CN114303210B

CN114303210B - Silicon transformer integrated chip

Info

Publication number: CN114303210B
Application number: CN202080061321.6A
Authority: CN
Inventors: 丹下贵之; 牛见义光
Original assignee: Murata Manufacturing Co Ltd
Current assignee: Murata Manufacturing Co Ltd
Priority date: 2019-10-08
Filing date: 2020-10-07
Publication date: 2025-03-21
Anticipated expiration: 2040-10-07
Also published as: WO2021071901A1; CN114303210A; US20220278041A1; US12148693B2

Abstract

A transformer includes a silicon substrate, a plurality of metal layers and a plurality of insulating layers laminated on the silicon substrate, a bottom winding of metal in contact with a first metal layer and a second metal layer of the plurality of metal layers, a first insulating layer on the bottom winding, a magnetic core on the first insulating layer, a second insulating layer on the magnetic core, a top winding of metal extending around the magnetic core and a portion of the second insulating layer, and a third insulating layer on the top winding. At least one of the top winding and the bottom winding is thicker than each of the plurality of metal layers.

Description

Silicon transformer integrated chip

Technical Field

The present invention relates to transformers. More particularly, the present invention relates to a transformer integrated into a silicon substrate that may be used in a DC-DC converter or power application.

Background

Conventional power supplies and DC-DC converters require large discrete magnetic components, such as transformers and inductors, that have inherent losses, heat generation, emit electromagnetic interference (EMI), and are costly to manufacture. Battery powered cell phones and hand held applications require small, efficient and cost effective components.

Accordingly, smaller magnetic assemblies and transformers have been developed that are fabricated directly on a substrate, such as a Printed Circuit Board (PCB) or a silicon substrate. Components such as planar inductors have been fabricated as semiconductor chips on the surface of a silicon substrate. These components have been fabricated similar to Integrated Circuits (ICs) using semiconductor fabrication techniques. However, as shown for example in WO publication 2016/209245, in a power management control IC with passive components, transformer windings in a metal layer on a silicon substrate are not suitable for high current operation, such as in a DC-DC converter application.

Disclosure of Invention

In order to overcome the above problems, preferred embodiments of the present invention provide a transformer integrated into a silicon substrate that can be used in high current DC-DC converter applications.

According to a preferred embodiment of the present invention, transformers are fabricated using an electroplated metal layer on a silicon substrate. The transformer including the magnetic core is manufactured through an electroplating process, unlike a conventional silicon process in which a transformer assembly is covered with an insulating material such as polyimide. In addition, the circuit on the primary side and the circuit on the secondary side of the transformer may coexist on the silicon substrate and may be electrically isolated from each other by the PN junction, which minimizes the distance between the primary circuit and the secondary circuit.

According to a preferred embodiment of the present invention, a transformer includes a silicon substrate, a plurality of metal layers and a plurality of insulating layers laminated on the silicon substrate, a first bottom winding of metal in contact with the first metal layer of the plurality of metal layers and a second bottom winding of copper in contact with the second metal layer of the plurality of metal layers, a first insulating layer on the first bottom winding and the second bottom winding, a magnetic core on the first insulating layer, a second insulating layer on the magnetic core, a first top winding and a second top winding of metal extending around a portion of the magnetic core and the second insulating layer, and a third insulating layer on the first top winding and the second top winding. At least one of the group consisting of the first top winding, the second top winding, the first bottom winding, and the second bottom winding is thicker than each of the plurality of metal layers.

The transformer may further comprise a circuit located on the silicon substrate, wherein the first bottom winding, the second bottom winding, the first top winding, the second bottom winding, and the magnetic core may be located on the same side of the silicon substrate as the circuit. The transformer may further include a PN junction in the silicon substrate that isolates the primary side and the secondary side of the transformer. The first bottom winding, the second bottom winding, the first top winding, and the second top winding may include an electroplated copper layer. The first top winding and the first bottom winding may define a primary winding and the second top winding and the second bottom winding define a secondary winding, which may be connected with respective ones of the plurality of metal layers and may not be electrically connected to each other.

According to a preferred embodiment of the present invention, a method of manufacturing a transformer includes providing a silicon substrate, laminating a plurality of metal layers and a plurality of insulating layers on the silicon substrate, electroplating copper to form a first bottom winding in contact with a first metal layer of the plurality of metal layers and a second bottom winding in contact with a second metal layer of the plurality of metal layers, forming a first insulating layer on the bottom winding, electroplating a magnetic core on the first insulating layer, forming a second insulating layer on the magnetic core, electroplating copper to form a first top winding and a second top winding on the second insulating layer, the first top winding and the second top winding extending around the magnetic core, and forming a third insulating layer on the first top winding and the second top winding.

At least one of the group consisting of the first top winding, the second top winding, the first bottom winding, and the second bottom winding may be thicker than each of the plurality of metal layers. The first top winding and the first bottom winding may define a primary winding, the second top winding and the second bottom winding define a secondary winding, and the primary winding and the secondary winding may be connected with respective ones of the plurality of metal layers and may not be electrically connected to each other.

According to a preferred embodiment of the invention, a transformer includes a first silicon substrate, a circuit on a first side of the first silicon substrate and including a plurality of metal layers, an oxide layer on a second side of the first silicon substrate, a second silicon substrate on the oxide layer, a bottom winding of metal on the second silicon substrate and connected to the circuit through the second silicon substrate, the oxide layer and the first silicon substrate, a first insulating layer on the bottom winding, a magnetic core on the first insulating layer, a second insulating layer on the magnetic core, a top winding of metal extending around the magnetic core and a portion of the second insulating layer and connected to the circuit through the second silicon substrate, the oxide layer and the first silicon substrate, and a third insulating layer on the top winding. At least one of the top winding and the bottom winding is thicker than each of the plurality of metal layers.

The transformer may further include a PN junction in the first silicon substrate and the second silicon substrate, the PN junction isolating a primary side and a secondary side of the transformer. The bottom winding and the top winding may comprise a plated copper layer. The top and bottom windings may define primary and secondary windings, which may be connected with respective ones of the plurality of metal layers and may not be electrically connected to each other.

According to a preferred embodiment of the present invention, a method of manufacturing a transformer includes providing a first silicon substrate, forming a circuit on a first side of the first silicon substrate, forming an oxide layer on a second side of the first silicon substrate, providing a second silicon substrate on the oxide layer, forming a via in the second silicon substrate, the oxide layer and the first silicon substrate, filling the via with a conductive metal in direct contact with the circuit, depositing metal on the second silicon substrate to form a bottom winding in contact with the conductive metal, forming a first insulating layer on the bottom winding, electroplating a magnetic core on the first insulating layer, forming a second insulating layer on the magnetic core, depositing metal to form a top winding on the second insulating layer and around the magnetic core in contact with the conductive metal, and forming a third insulating layer on the top winding.

The step of forming the circuit may include forming a plurality of metal layers, and at least one of the top winding and the bottom winding may be thicker than each of the plurality of metal layers. The top and bottom windings may define primary and secondary windings, which may be connected with respective ones of the plurality of metal layers and may not be electrically connected to each other. The metal may be electroplated copper.

According to a preferred embodiment of the invention, a transformer includes a silicon substrate, a circuit on a first side of the silicon substrate and including a plurality of metal layers, a bottom winding of metal on a second side of the silicon substrate and in contact with the circuit through the silicon substrate, a first insulating layer on the bottom winding, a magnetic core on the first insulating layer, a second insulating layer on the magnetic core, a top winding of metal surrounding a portion of the magnetic core and the second insulating layer and in contact with the circuit through the silicon substrate, and a third insulating layer on the top winding. At least one of the top winding and the bottom winding is thicker than each of the plurality of metal layers.

The transformer may further include a PN junction in the silicon substrate that isolates a primary side of the transformer from a secondary side. The bottom winding and the top winding may comprise a plated copper layer. The top and bottom windings may define primary and secondary windings, which may be connected with respective ones of the plurality of metal layers and may not be electrically connected to each other.

According to a preferred embodiment of the present invention, a method of manufacturing a transformer includes providing a silicon substrate, forming a circuit on a first side of the silicon substrate, forming a via in the silicon substrate, filling the via with a conductive metal in direct contact with a metal layer of the circuit, depositing metal on a second side of the silicon substrate to form a bottom winding in contact with the conductive metal, forming a first insulating layer on the bottom winding, electroplating a magnetic core on the first insulating layer, forming a second insulating layer on the magnetic core, depositing metal to form a top winding on the second insulating layer and around the magnetic core in contact with the conductive metal, and forming a third insulating layer on the top winding.

At least one of the top and bottom windings may be thicker than any metal layer formed on the silicon substrate. The top and bottom windings may define primary and secondary windings, and the primary and secondary windings may not be electrically connected to each other.

According to a preferred embodiment of the invention, an electronic component comprises a redistribution layer comprising a metal layer and an insulating layer, a silicon substrate comprising a first transistor and a second transistor, and a magnetic component comprising a first metal winding extending around a magnetic core and connected to the metal layer. The first metal winding is thicker than the metal layer.

The electronic component may further comprise a PN junction between the first transistor and the second transistor. The electronic assembly may further include a silicon via extending through at least a portion of the silicon substrate and connecting the metal layer with the first metal winding. A portion of the first metal winding may be in direct contact with the silicon substrate. The redistribution layer and the magnetic component may be located on opposite sides of the silicon substrate or may be located on the same side of the silicon substrate. The magnetic component may be a transformer and may further include a second metal winding that may extend around the magnetic core and may not be electrically connected to the first metal winding. The first transistor may be connected to the first metal winding and the second transistor may be connected to the second metal winding. The first and second metal windings may be electrically isolated from each other. The magnetic component may be an inductor. The second metal winding may be thicker than the metal layer. The second metal winding may comprise a plated copper layer. The first metal winding may include a plated copper layer.

According to a preferred embodiment of the present invention, a transformer includes a silicon substrate, an insulating layer on the silicon substrate and including a plurality of metal layers, a magnetic core, a bottom winding of metal extending below the magnetic core and in contact with a first metal layer and a second metal layer of the plurality of metal layers, and a top winding of metal extending around the magnetic core. At least one of the top winding and the bottom winding is thicker than each of the plurality of metal layers.

The transformer may also include circuitry located on the silicon substrate, wherein the bottom winding, the top winding, and the magnetic core may be located on the same side of the silicon substrate as the circuitry. The transformer may further include a PN junction in the silicon substrate that isolates the primary side and the secondary side of the transformer. The bottom winding and the top winding may comprise a plated copper layer. The top and bottom windings may define primary and secondary windings, which may be connected with respective ones of the plurality of metal layers and may not be electrically connected to each other. The metal may be copper.

According to a preferred embodiment of the invention, a transformer includes a silicon substrate including an oxide layer, a circuit located on a first side of the silicon substrate and including a plurality of metal layers, and an insulating layer located on a second side of the silicon substrate and including a magnetic core, a bottom winding of metal extending below the magnetic core and connected to the circuit through the silicon substrate and the oxide layer, and a top winding of metal extending around the magnetic core and connected to the circuit through the silicon substrate and the oxide layer. At least one of the top winding and the bottom winding is thicker than each of the plurality of metal layers.

According to a preferred embodiment of the invention, a transformer includes a silicon substrate, a circuit on a first side of the silicon substrate and including a plurality of metal layers, and an insulating layer on a second side of the silicon substrate and including a magnetic core, a bottom winding of metal extending below the magnetic core and in contact with the circuit through the silicon substrate, and a top winding of metal extending around the magnetic core and in contact with the circuit through the silicon substrate. At least one of the top winding and the bottom winding is thicker than each of the plurality of metal layers.

The above and other features, elements, characteristics, steps and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments thereof with reference to the attached drawings.

Drawings

Fig. 1 shows a transformer in a circuit according to a preferred embodiment of the invention.

Fig. 2 to 25 show process steps for manufacturing the transformer shown in fig. 1.

Fig. 26 shows a transformer in a circuit according to another preferred embodiment of the invention.

Fig. 27 to 46 show process steps for manufacturing the transformer of fig. 26 according to a preferred process of the present invention.

Fig. 47 shows a transformer in a circuit according to another preferred embodiment of the invention.

Fig. 48 to 67 show process steps for manufacturing the transformer of fig. 47 according to a preferred process of the present invention.

Fig. 68 shows a process of manufacturing photosensitive polyimide as an insulating layer.

Detailed Description

Transformers integrated into the silicon substrate allow increasing the thickness of the winding metal. Thus, the transformer can transmit increased current while maintaining a small physical size. Thus, the transformer may be used for smaller volume, higher power applications.

Fig. 1 shows a transformer 100 in a circuit on a silicon substrate 110 according to a preferred embodiment of the invention. Fig. 1 is a cross-section of a portion of a circuit. Fig. 1 shows that the silicon substrate 110 may include doped regions defining a source S and a drain D, and a metal layer (e.g., within a dashed oval) defining a gate G of the transistor 130. The transistors may be interconnected by a metal layer 140 within the insulating material 120 on the silicon substrate 110. The metal layer 140 may be formed using typical semiconductor processing techniques. The transformer 100 includes copper plated metal windings 150 wound around a magnetic core 160. The metal winding 150 is connected to the metal layer 140. The metal winding 150 may include a primary winding and a secondary winding that are not physically connected to each other. For example, the primary winding may be connected to the metal layer 140 on the first side of the transformer 100 and may not be connected on the second side of the transformer 100 with an insulating material between the primary winding and the metal layer 140, and the secondary winding may be connected to the metal layer 140 on the second side of the transformer 100 and may not be connected on the first side of the transformer 100 with an insulating material between the secondary winding and the metal layer 140. Thus, the primary winding and the secondary winding are not physically connected to each other. As shown in fig. 1, the primary and secondary windings may not be connected to the metal layer 140 in some areas between the metal layers 140, such as at the isolation points 125.

The metal winding 150 is thicker than the metal layer 140, which allows the metal winding 150 to transmit higher currents. For example, the thickness of the metal winding 150 may be about 40 μm to about 60 μm within manufacturing tolerances, and each metal layer may be up to about 3 μm within manufacturing tolerances. The core 160 may be made of a cobalt alloy such as CoNiFe, coFeSi, coZrO, coZrTa, of a soft alloy such as Ni, fe, niFe, or of any suitable magnetic material.

Although fig. 1 shows a single cross section of transformer 100, it should be understood that metal winding 150 includes a primary winding connected to a primary circuit, and a secondary winding connected to a secondary circuit. The primary and secondary windings are not connected to each other to provide isolation between the primary and secondary sides of the transformer 100. An inductor may be used instead of the transformer 100, wherein the metal winding 150 is a single winding.

Fig. 1 shows a PN junction 180 (within the dashed box) in a silicon substrate 110 for isolating the circuit between the primary side and the secondary side of the transformer 100. For example, the power transistor on the primary side may be defined by the transistor on the left side of fig. 1, and the synchronous rectifier on the secondary side may be defined by the transistor on the right side of fig. 1. As shown, solder balls 190 may be used to interconnect the integrated circuit with a power supply, control signals, external circuitry, etc., although other interface features and techniques are possible.

Fig. 2-25 illustrate successive process steps that may be used to fabricate the transformer 100 shown in fig. 1. The description of the features previously described with respect to fig. 1 may be omitted for brevity.

Fig. 2 shows a circuit comprising a plurality of insulating layers 220 (shown as a bulk material since each of the plurality of insulating layers 220 may not be distinguishable from one another after lamination) laminated together, and a metal layer 240 comprising a redistribution layer (RDL) 242 formed on a silicon substrate 210 using conventional semiconductor processing techniques. Fig. 2 also shows that spacer dots 225 of insulating material are formed in the portion between metal layer 240 and RDL 242. Fig. 3 shows a first seed metal 342 formed on the RDL. For example, the seed metal may be Ni, cr, au, cu, or any other suitable material that may be deposited or electroplated on top of the RDL. Fig. 4 shows a patterned resist film 480, the patterned resist film 480 covering a portion of the first seed metal 442 and exposing a portion of the first seed metal 442.

Fig. 5 shows a bottom winding layer 552 of the transformer formed by electrolytic plating (electrolytically plating) of copper on the exposed portion of the first seed metal 542. Although fig. 5 shows a single cross section, it should be appreciated that a plurality of electrically isolated bottom winding layers are formed. The bottom winding layer may be formed in a single step or multiple steps. In a transformer, some bottom winding layers define a portion of a primary winding and some bottom winding layers define a portion of a secondary winding. In an inductor, the bottom winding layer defines a portion of the inductor winding. In the step shown in fig. 6, the resist film is stripped, exposing the first seed metal 642 and the bottom winding layer 652. Fig. 7 shows that the first seed metal 742, which is not covered by the bottom winding layer 752, is etched away. The portion of the windings of the transformer or inductor defined by the bottom winding layer 752, and the remaining portion of the first seed metal 742 are in direct contact with the top metal layer 740 and the top insulating layer 720.

Fig. 8 shows that an insulating layer 820 is formed over and around the patterned first seed metal 842 and bottom winding layer 852. Fig. 68 shows a process of manufacturing photosensitive polyimide (PSPI) as an insulating layer. Fig. 68 shows the formation of an insulating layer by (1) coating an uncured positive or negative PSPI 5 on a substrate 10, (2) patterning the coated uncured PSPI 15 with Ultraviolet (UV) radiation through a mask 90, (3) developing the irradiated, coated, uncured PSPI 25 to produce a patterned positive or negative image of the mask 90, and (4) curing the patterned PSPI 35 by heat treatment. The insulating layer 820 in fig. 8 may be polyimide, su-9, phenolic resist, or any other suitable material. Fig. 9 illustrates the formation of a second seed metal 944 over insulating layer 920. Fig. 10 shows that a patterned resist film 1080 is formed over the second seed metal 1044, thereby exposing a portion of the second seed metal 1044.

Fig. 11 illustrates the formation of the magnetic core 1160 by electroplating any of the materials previously described over the exposed portion of the second seed metal 1144. In the step shown in fig. 12, the resist film is peeled off, exposing the magnetic core 1260 and the second seed metal 1244. Fig. 13 shows that the second seed metal 1344 not covered by the core 1360 is etched away.

Fig. 14 shows an insulating layer 1420 formed over and around patterned second seed metal 1444 and magnetic core 1460 using the process previously described with respect to fig. 68. Fig. 15 shows the formation of a third seed metal 1546 over the insulating layer 1520. Fig. 16 shows that a patterned resist film 1680 is formed over the third seed metal 1646, exposing a portion of the third seed metal 1646.

Fig. 17 shows the formation of top winding layer 1754 by electrolytic plating of copper onto the exposed sections of third seed metal 1746. Although fig. 17 shows a single cross section, it should be appreciated that top winding layer 1754 is connected to a different bottom winding layer. The plurality of top winding layers may be formed in one step or in multiple steps. In a transformer, some top winding layers define a portion of a primary winding and some top winding layers define a portion of a secondary winding. In an inductor, the top winding layer defines a portion of the inductor winding. In the step shown in fig. 18, the resist film is stripped, exposing the third seed metal 1846 and the top winding layer 1854. Fig. 19 shows that the third seed metal not covered by the top winding layer 1954 is etched away.

Fig. 20 shows the formation of an insulating layer 2020 on and around top winding layer 2054 using the process described with respect to fig. 68. In addition to covering the top winding layer 2054, the insulating layer 2020 may also include wells capable of forming interconnect pads. Fig. 21 illustrates the formation of a fourth seed metal 2148 over insulating layer 2120. Fig. 22 shows that a patterned resist film 2280 is formed over the fourth seed metal 2248, exposing a portion of the fourth seed metal 2248 in the area where the interconnect pad is to be provided.

Fig. 23 shows that interconnect pads 2392 are formed by electroplating electroplating copper on the portions of the fourth seed metal 2348 exposed by the resist film 2380. Although fig. 23 shows that only two interconnect pads 2392 are formed, any number of interconnect pads may be formed. In the step shown in fig. 24, the resist film is peeled off, and the fourth seed metal 2448 not covered by the interconnect pad 2492 is etched. Fig. 25 illustrates that solder balls 2590 may be formed on interconnect pads 2592.

Fig. 26 shows a transformer 2600 in a circuit on a silicon substrate according to another preferred embodiment of the invention. Fig. 26 is a cross-section of a portion of a circuit. In the present embodiment, the substrates include a first silicon substrate 2610, a second silicon substrate 2612, and a Buried Oxide (BOX) layer 2615 between the first silicon substrate 2610 and the second silicon substrate 2612. Similar to the preferred embodiment shown in fig. 1, fig. 26 shows that the first silicon substrate 2610 can include doped regions defining a source S and a drain D, and a metal layer (e.g., within a dashed oval) defining a gate G of a transistor 2630. The transistor 2630 may be interconnected by laminating a metal layer 2640 and an insulating layer 2620 on the first silicon substrate 2610. The metal layer 2640 is formed using typical semiconductor processing techniques. Transformer 2600 includes copper plated metal windings 2650 wound around magnetic core 2660. The metal windings 2650 are connected to the circuit through the metal layer 2670. The metal winding 2650 is thicker than the metal layer 2640, having a thickness as previously described, which allows the metal winding 2650 to transmit higher currents. Core 2660 may comprise any of the materials previously described.

Although fig. 26 shows a single cross section of transformer 2600, it should be understood that metal winding 2650 includes a primary winding connected to a primary circuit and a secondary winding connected to a secondary circuit, where the primary and secondary windings are not physically connected to each other, which provides isolation between the primary and secondary sides of transformer 2600. In addition, portions of the metal windings 2650 may not be connected to the metal layers 2640, wherein adjacent metal layers 2640 are separated by isolation points 2622 made of an insulating material, the isolation points 2622 providing isolation between adjacent metal layers 2640. The cross-section shown in fig. 26 represents a portion where the metal winding 2650 is connected to the primary side of the transformer (i.e., the left side of fig. 26) and a portion where the metal winding 2650 is connected to the secondary side of the transformer (i.e., the right side of fig. 26). An inductor may be used in place of transformer 2600, where metal winding 2650 is a single winding.

Fig. 26 shows a PN junction 2680 (within the dashed box) in the first silicon substrate 2610 for isolating the circuit between the primary side and the secondary side of the transformer 2600. For example, the power transistor on the primary side may be defined by the transistor on the left side of fig. 26, and the synchronous rectifier on the secondary side may be defined by the transistor on the right side of fig. 26. As shown, solder balls 2690 may be used to interconnect the integrated circuit with power supplies, control signals, external circuitry, and the like, although other interface features and techniques are possible.

In the preferred embodiment, the transformer 2600 is formed on the opposite side of the first and second silicon substrates 2610 and 2612 from the circuit, and is connected to the circuit through a Through Silicon Via (TSV) 2675 and is covered by an insulating layer 2625. Although only two TSVs 2675 are shown in fig. 26, any number of TSVs 2675 may be used. Typically, each winding of a transformer or inductor will include two TSVs. Additional TSVs may be used, for example, if the winding includes a center tap. As mentioned, the first silicon substrate 2610 and the second silicon substrate 2012 may include a BOX layer 2615 therebetween, which may help to fabricate the TSV 2675.BOX layer 2615 may help fabricate TSV 2675, as shown in fig. 26, BOX layer 2615 does not extend all the way through first silicon substrate 2610. If a TSV is used that extends all the way through the first silicon substrate 2610, a BOX layer may not be used.

The silicon structure on the BOX layer reduces parasitic capacitance generated in the circuit and is suitable for higher operating frequencies and higher performance. In addition, the current path from the active silicon layer to the transformer through the TSV 2675 is relatively short compared to a configuration with a thicker silicon substrate, which helps to improve circuit efficiency. The shorter TSVs 2675 provide greater design layout flexibility and smaller circuit layout. Thus, this smaller configuration has better efficiency and can operate at higher frequencies than a similar structure without the BOX layer.

Fig. 27 to 46 show successive processing steps included in manufacturing the transformer 2600 shown in fig. 26. Descriptions of the previously described features may be omitted for brevity.

Fig. 27 shows a circuit including an insulating layer 2720 and a metal layer 2740 over a first silicon substrate 2710. Insulating layer 2720 and metal layer 2740 define an RDL. The silicon layer 2710 may be formed on RDL using a conventional silicon-on-insulator (SOI) process. BOX layer 2715 and second silicon substrate 2712 may be formed using a conventional process. Fig. 28 shows a patterned resist film 2880, the patterned resist film 2880 covering a portion of the second seed metal 2812 and exposing a portion of the second seed metal 2812. Fig. 29 shows that the exposed portion of the second silicon substrate 2912 and the BOX layer 2915 underlying the exposed portion are etched to define a contact hole CH through the second silicon substrate 2912 and the BOX layer 2915, thereby exposing a portion of the first silicon substrate 2910. The BOX layer 2915 may be used to form a contact hole CH extending only through the second silicon substrate 2912.

In the step shown in fig. 30, the resist film is peeled off, leaving a contact hole CH in the second silicon substrate 3012 and BOX layer 3015. Fig. 31 shows that a first seed metal 3142 is formed on the second silicon substrate 3112 and in the contact hole CH so as to be in contact with the BOX layer 3115 and portions of the first silicon substrate 3110. Materials for the seed metal may include those previously described. Fig. 32 shows a patterned resist film 3280, the patterned resist film 3280 covering a portion of the first seed metal 3242 and exposing a portion of the first seed metal 3242 in the contact hole CH.

Fig. 33 shows TSV 3375 formed by electrolytic plating copper onto the exposed portion of first seed metal 3242 in contact hole CH. In the step shown in fig. 34, the resist film is stripped to expose the first seed metal 3442 and the TSV 3475. Fig. 35 shows a patterned resist film 3580, the patterned resist film 3580 covering a portion of the first seed metal 3542 and exposing a portion of the first seed metal 3542 between TSVs 3575.

Fig. 36 shows that a bottom winding layer 3652 of the transformer is defined by electrolytic plating copper over the exposed portion of the first seed metal 3642 and the TSV 3675. In the step shown in fig. 37, the resist film is stripped and the exposed portions of the first seed metal are etched away, leaving the bottom winding layer 3752. The portion of the windings of the transformer or inductor defined by the bottom winding layer 3752, and the remaining portion of the first seed metal 3742 are in direct contact with the second silicon substrate 3712. Although fig. 37 shows a single cross section, it should be understood that a plurality of electrically isolated bottom winding layers are formed. The bottom winding layer may be formed in a single step or in multiple steps. In a transformer, some bottom winding layers define a portion of a primary winding and some bottom winding layers define a portion of a secondary winding. In an inductor, the bottom winding layer defines a portion of the inductor winding. Fig. 38 shows that an insulating layer 3820 is formed on and around the bottom winding layer 3852 by heat treatment.

Fig. 39 shows that a second seed metal 3944 is formed over the insulating layer 3920, and a patterned resist film 3980 is formed over the second seed metal 3944. Fig. 40 shows the formation of a magnetic core 4060 by electroplating an exposed portion of a second seed metal 4044. In the step shown in fig. 41, the resist film is peeled off to expose the magnetic core 4160, and the exposed portion of the second seed metal is etched away.

Fig. 42 shows an insulating layer 4220 formed over and around the patterned second seed metal 4244 and magnetic core 4260 using the process previously described with respect to fig. 68. Fig. 43 shows that a third seed metal 4346 is formed over the insulating layer 4320 and a patterned resist film 4380 is formed over the third seed metal 4346, exposing a portion of the third seed metal 4346.

Fig. 44 shows a bottom winding layer 4454 of a transformer formed by electrolytic plating copper on the exposed portion of the third seed metal 4446. Although fig. 44 shows a single cross section, it should be understood that top winding layer 4454 is connected to a different bottom winding layer. The plurality of top winding layers may be formed in one step or in multiple steps. In a transformer, some top winding layers define a portion of a primary winding and some top winding layers define a portion of a secondary winding. In an inductor, the top winding layer defines a portion of the inductor winding. In the step shown in fig. 45, the resist film is stripped, and the exposed third seed metal is etched, thereby exposing the top winding layer 4554.

Fig. 46 shows an insulating layer 4620 formed over and around top winding layer 4654 to insulate and protect transformer 4600 using the process described with respect to fig. 68. Although not shown, interconnect pads and solder balls may be formed to interconnect the circuits with power supplies, control signals, other circuits, etc. in the manner previously described.

Fig. 47 shows a transformer 4700 in a circuit on a silicon substrate in accordance with another preferred embodiment of the present invention. Fig. 47 is a cross-section of a portion of a circuit. Similar to the preferred embodiment shown in fig. 26, fig. 47 shows that the first silicon substrate 4710 may include doped regions defining the source S and drain D and a metal layer defining the gate G of the transistor 4730 (e.g., within a dashed oval). The transistor 4730 may be interconnected by a metal layer 4740 within the insulating material 4720 on the silicon substrate 4710. The metal layer 4740 is formed using typical semiconductor processing techniques. The transformer 4700 includes copper plated metal windings 4750 wound around a magnetic core 4760. The metal winding 4750 is connected to the circuit through the metal layer 4770. The metal winding 4750 is thicker than the metal layer 4740, having a thickness as previously described, which allows the metal winding 4750 to transmit higher currents. The magnetic core 4760 may comprise any of the materials previously described.

Although fig. 47 shows a single cross section of transformer 4700, it should be appreciated that metal winding 4750 includes a primary winding connected to a primary circuit and a secondary winding connected to a secondary circuit, wherein the primary and secondary windings are not physically connected to each other, which provides isolation between the primary and secondary sides of transformer 4700. In addition, portions of the metal windings 4750 may not be connected to adjacent metal layers 4740, wherein adjacent metal layers 4740 are separated by isolation points 4722 made of an insulating material, the isolation points 4722 providing isolation between adjacent metal layers 4740. The cross-section shown in fig. 47 represents the portion of the metal winding 4750 connected to the primary side of the transformer (i.e., the left side of fig. 47) and the portion of the metal winding 4750 connected to the secondary side of the transformer (i.e., the right side of fig. 47). An inductor may be used in place of transformer 4700, wherein metal winding 4750 is defined by a single winding.

Fig. 47 shows a PN junction 4780 (within the dashed box) in a silicon substrate 4710 for isolating the circuit between the primary side and the secondary side of a transformer 4700. For example, the power transistor on the primary side may be defined by the transistor on the left side of fig. 47, and the synchronous rectifier on the secondary side may be defined by the transistor on the right side of fig. 47. Solder balls 4790 may be used to interconnect the integrated circuit with power supplies, control signals, external circuitry, etc., although other interface features and techniques are possible.

However, as in the transformer 2600 shown in fig. 26, a transformer 4700 is formed on the opposite side of the silicon substrate 4710 from the circuit, connected to the circuit through the TSV 4775, and covered with an insulating layer 4725. Thus, the silicon process may be used to fabricate the transformer circuitry without the additional steps or expense associated with the BOX and the second silicon layer. In the preferred embodiment, TSV 4775 is directly connected to metal layers within the circuit. Although only two TSVs 4775 are shown in fig. 47, any number of TSVs 4775 may be used. Typically, each winding of a transformer or inductor will include two TSVs. Additional TSVs may be used, for example, if the winding includes a center tap. Since TSV 4475 extends all the way through silicon substrate 4710, no BOX layer is required.

Fig. 48 to 67 show processing steps included in manufacturing the transformer 4700 shown in fig. 47. Descriptions of the previously described features may be omitted for brevity.

Fig. 48 shows a circuit including an insulating layer 4810 and a metal layer 4810 over a first silicon substrate 4810. Insulating layer 4820 and metal layer 4840 define RDL. The silicon layer 4810 may be formed on RDL using a conventional silicon-on-insulator (SOI) process. Fig. 49 shows a patterned resist film 4980, the patterned resist film 4980 covering a portion of the silicon substrate 4910 and exposing a portion of the silicon substrate 4910. Fig. 50 shows that the exposed portion of the silicon substrate 5010 and the portion of the insulating layer 5020 underlying the exposed portion of the silicon substrate 5010 are etched to expose the metal layer 5040 and define a contact hole CH through the silicon substrate 5010 and the insulating layer 5020.

In the step shown in fig. 51, the resist film is peeled off, leaving the contact hole CH in the silicon substrate 5110. Fig. 52 shows that a first seed metal 5242 is formed on the silicon substrate 5210 and in the contact hole CH to contact the metal layer 5240. Fig. 53 shows that a patterned resist film 5380 is formed to cover a portion of the first seed metal 5342 and to expose a portion of the first seed metal 5342 in the contact hole CH.

Fig. 54 shows the formation of TSV 5475 by electrolytic plating copper onto the exposed portion of first seed metal 5442 in contact hole CH. In the step shown in fig. 55, the resist film is stripped to expose the first seed metal 5542 and the TSV 5575. Fig. 56 shows that a patterned resist film 5680 is formed to cover a portion of the first seed metal 5642 and expose a portion of the first seed metal 5642 in the region around the TSV 5675.

Fig. 57 shows a bottom winding layer 5752 of a transformer formed by electrolytic plating copper on the first seed metal 5742 and the exposed portion of the TSV 5575. In the step shown in fig. 58, the resist film is stripped and the exposed portion of the first seed metal is etched away, leaving the bottom winding layer 5852. The winding portion of the transformer or inductor defined by the bottom winding layer 5852 and the remaining portion of the first seed metal 5842 are in direct contact with the silicon substrate 5810. Although fig. 58 shows a single cross section, it should be understood that a plurality of electrically isolated bottom winding layers are formed. The bottom winding layer may be formed in a single step or multiple steps. In a transformer, some bottom winding layers define a portion of a primary winding and some bottom winding layers define a portion of a secondary winding. In an inductor, the bottom winding layer defines a portion of the inductor winding. Fig. 59 shows that an insulating layer 5920 is formed on and around bottom winding layer 5952 to expose portions of bottom winding layer 5952 using the process previously described with respect to fig. 68.

Fig. 60 shows that a second seed metal 6044 is formed over the insulating layer 6020, and a patterned resist film 6080 is formed over the second seed metal 6044. Fig. 61 illustrates a magnetic core 6160 formed by electroplating any of the materials previously described over the exposed portion of the second seed metal 6144. In the step shown in fig. 62, the resist film is peeled off to expose the magnetic core 6260, and the exposed second seed metal is etched away.

Fig. 63 illustrates the formation of an insulating layer 6320 on and around patterned second seed metal 6344 and magnetic core 6360 using the process previously described with respect to fig. 68. Fig. 64 shows that a third seed metal 6446 is formed over the insulating layer 6420 and a patterned resist film 6480 is formed over the third seed metal 6446, exposing a portion of the third seed metal 6446.

Fig. 65 shows the formation of the bottom winding layer 6554 of the transformer by electrolytic plating of copper on the exposed portion of the first seed metal 6546. Although fig. 65 shows a single cross section, it should be understood that top winding layer 6554 is connected to a different bottom winding layer. The plurality of top winding layers may be formed in one step or in multiple steps. In a transformer, some top winding layers define a portion of a primary winding and some top winding layers define a portion of a secondary winding. In an inductor, the top winding layer defines a portion of the inductor winding. In the step shown in fig. 66, the resist film is peeled off, and the exposed third seed metal is etched, thereby exposing the top winding layer 6654.

Fig. 67 shows an insulating layer 6720 formed around the top winding layer 6754 to insulate and protect the transformer 6700 using the process previously described with respect to fig. 68. Although not shown, interconnect pads and solder balls may be formed to interconnect with circuitry on the opposite substrate side of transformer 6700.

It should be understood that the foregoing description is only illustrative of the invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variances which fall within the scope of the appended claims.

Claims

1. A transformer, comprising:

A silicon substrate;

A plurality of metal layers and a plurality of insulating layers laminated on the silicon substrate;

a first bottom winding of metal and a second bottom winding of copper, the first bottom winding being in contact with a first metal layer of the plurality of metal layers and the second bottom winding being in contact with a second metal layer of the plurality of metal layers;

A first insulating layer on the first bottom winding and the second bottom winding;

A magnetic core on the first insulating layer;

a second insulating layer on the magnetic core;

a first top winding and a second top winding of the metal extending around a portion of the magnetic core and the second insulating layer, and

A third insulating layer on the first and second top windings, wherein

At least one of the group comprising the first top winding, the second top winding, the first bottom winding and the second bottom winding is thicker than each of the plurality of metal layers, wherein,

The first top winding and the first bottom winding define a primary winding;

the second top winding and the second bottom winding defining a secondary winding, and

The primary winding and the secondary winding are connected with respective ones of the plurality of metal layers and are not electrically connected with each other.

2. The transformer of claim 1, further comprising circuitry on the silicon substrate, wherein

The first bottom winding, the second bottom winding, the first top winding, the second top winding, and the magnetic core are on the same side of the silicon substrate as the circuit.

3. The transformer of claim 1 or 2, further comprising a PN junction in the silicon substrate, the PN junction isolating a primary side and a secondary side of the transformer.

4. The transformer of one of claims 1 to 3, wherein the first bottom winding, the second bottom winding, the first top winding, and the second top winding comprise a plated copper layer.

5. Transformer according to one of claims 1 to 4, wherein the metal is copper.

6. A method of manufacturing a transformer, the method comprising:

Providing a silicon substrate;

laminating a plurality of metal layers and a plurality of insulating layers on the silicon substrate;

Electroplating copper to form a first bottom winding in contact with a first metal layer of the plurality of metal layers and a second bottom winding in contact with a second metal layer of the plurality of metal layers;

forming a first insulating layer on the bottom winding;

electroplating a magnetic core on the first insulating layer;

Forming a second insulating layer on the magnetic core;

Electroplating copper to form a first top winding and a second top winding on the second insulating layer, the first top winding and the second top winding extending around the magnetic core, and

Forming a third insulating layer over the first top winding and the second top winding, wherein,

The first top winding and the first bottom winding define a primary winding;

7. The method of claim 6, wherein at least one of the group consisting of the first top winding, the second top winding, the first bottom winding, and the second bottom winding is thicker than each of the plurality of metal layers.